1. Field of the Invention
This invention relates to a heat exchanger for conducting heat-exchange by using a thermoelectric conversion element.
2. Description of the Related Art
A heat exchanger for temperature-controlling a cooling medium or a chemical solution by using thermoelectric conversion elements is known. FIG. 6 of the accompanying drawings is a sectional view of a heat exchanger disclosed in Japanese Patent Laid-Open Publication No. 242022/1996.
In the drawing, the heat exchanger 1 includes a heat-absorbing body 3 made of aluminum, heat radiation fins 19 and electronic cooling element groups 2 (hereinafter called xe2x80x9cthermoelectric conversion element modulesxe2x80x9d) sandwiched between the heat absorbing body 3 and the heat radiation fins 19. The thermoelectric heat conversion element module 2 includes a large number of p- and n-type thermoelectric conversion elements 12 and 13 that are mutually connected by electrodes 20 on a heat absorption side and electrodes 14 on a heat radiation side, each made of copper, for example.
Thin insulating layers 16 each made of alumina are formed by anodic oxidation on the surface of the heat absorbing body 3 and the heat radiation fins 19 that oppose the thermoelectric conversion element module 2 in order to insulate mutually the electrodes 14, 14 on the heat radiation side and the electrodes 20 and 20 on the heat absorption side. Silicon grease 21 or an adhesive having high thermal conductivity is interposed between the insulating layer 16 and the electrode 14 and between the insulating layer 16 and the electrode 20.
When a current is caused to flow through the thermoelectric conversion element module 2 in such a heat exchanger 1, a temperature difference occurs between the electrodes 14 and 20 of the thermoelectric conversion element module 2, and heat exchange is executed between the heat absorbing body 3 and the heat radiation fins 19.
However, this prior art technology is not yet free from the following problems.
The grease 21 or the adhesive is interposed between the insulating layer 16 and the electrode 14 and between the insulating layer 16 and the electrode 20. Though the grease 21 or the adhesive has higher thermal conductivity than that of the ordinary type, its thermal resistance is greater than those of the insulating layer 16 and the metals. In other words, its thermal resistance is high, so that a heat loss develops during heat exchange and heat exchange efficiency decreases.
In consequence, performance of the heat exchangeability decreases, and the heat exchanger fails to control the cooling medium or the chemical solution to a desired temperature or needs greater electric power so as to control them to a desired temperature.
To solve the problems described above, it is an object of the present invention to provide a heat exchanger having small thermal resistance but high efficiency.
In a heat exchanger for executing heat exchange between heat exchange bodies on a heat radiation side and heat exchange bodies on a heat absorption side, the first invention of this invention for accomplishing the object described above includes the heat exchange bodies on the heat radiation side and the heat exchange bodies on the heat absorption side each being disposed hierarchically, and thermoelectric conversion element modules, each being interposed between the heat exchange body on the heat radiation side and the heat exchange body on the heat absorption side through an insulating coat, and having a plurality of thermoelectric conversion elements, wherein the insulating coat is formed integrally on a surface of the heat exchange bodies on at least one of the heat radiation side and the heat absorption side, and a metal coat keeping electric contact with the surface of the thermoelectric conversion elements on either the heat radiation side or the heat absorption side is integrally formed on the insulating coat.
According to the first invention, the insulating coat and the metal coat are integrally formed on the surface of the heat exchange bodies on at least one of the sides, and the thermoelectric conversion elements are brought into electric contact. In this way, coupling can be achieved without applying a material having low thermal conductivity such as grease to the contact surface between the heat exchange body and the thermoelectric conversion element. Therefore, heat does not pass through the material having low thermal conductivity, and adhesion between them can be improved, lowering thereby thermal resistance. In other words, the heat exchanger has improved performance of heat conduction and can execute more efficiently heat exchange with lower power consumption. The heat exchanger can also execute accurately temperature control.
In the heat exchanger of the first invention described above, the second invention of this invention employs a construction in which electrodes of opposing thermoelectric conversion element modules are fixed to the metal coat formed integrally on the insulating coat.
According to the second invention, the electrodes of the thermoelectric conversion element modules that are produced separately are fixed to the insulating coat and the metal coat formed integrally with the heat exchange body. In other words, it is technically difficult to form the metal coat, to be formed on the insulating coat, to a thickness sufficient for use as the electrode of the thermoelectric conversion element module, and the cost is high, too. Therefore, the production of the heat exchanger becomes easier when the electrodes are separately produced and are fixed to the metal coat.
Since both electrodes and metal coat are made of metal, they can be fixed to each other while keeping high adhesion and thermal resistance is small on their contact surface. Moreover, when fixing is made by metal fusion such as soldering, for example, the solder is a metal and has high thermal conductivity, and can firmly couple them together. In consequence, the thermal contact resistance becomes smaller at the contact positions between the heat exchange body and the thermoelectric conversion element module, performance of heat conduction of the heat exchanger can be improved, and heat exchange can be executed more efficiently with smaller power consumption. When temperature control is conducted in this heat exchanger, control can be conducted more accurately.
Soldering is carried out at a relatively low temperature and does not invite problems such as thermal deformation of the heat exchange body and peel of brazing inside the heat exchange body. Therefore, fixing can be conducted with high reliability.
The heat exchanger according the third invention provides a heat exchanger wherein the heat exchange body on the heat radiation side and the electrode on the heat radiation side are fixed to one another by soldering, grease having high thermal conductivity is interposed between the heat exchange body on the heat absorption side and the electrode on the heat absorption side, and they are then brought into adhesion with one another.
According to the third invention, the heat exchange body on the heat radiation side and the electrode on the heat radiation side are fixed to one another by soldering, and grease having high thermal conductivity is interposed between the heat exchange body on the heat absorption side and the electrode on the heat absorption side. The effect brought forth by fixing and soldering the heat exchange body on the heat radiation side and the electrode on the heat radiation side is the same as that of the second invention.
When the heat exchanger cools a chemical solution, or the like, flowing through the heat exchange body on the heat absorption side, calories (heat) flowing from the thermoelectric conversion element module to the heat exchange body on the heat radiation side becomes greater than calories (heat) flowing from the heat exchange body on the heat absorption side to the thermoelectric conversion element module. Therefore, soldering is made on the side in which the flowing calories are greater, so as to improve adhesion of that portion. In consequence, the thermal resistance can be reduced.
The heat exchange body on the heat absorption side and the thermoelectric conversion element module are brought into mutual contact while interposing grease between them, and are allowed to slide while keeping their adhesion. Even when the temperature difference becomes great between the heat exchange body on the heat radiation side and the heat exchange body on the heat absorption side and the degrees of their expansion becomes different, the heat exchange body on the heat absorption side and the thermoelectric conversion element module are slidable due to the grease. Consequently, since any force causing distortion of the thermoelectric conversion element modules does not act, the thermoelectric conversion element module is not broken and performance of thermal conduction does not decrease, either.